It is well documented that endotoxins can elicit birth complications in pregnant animals and humans. These complications include spontaneous abortions, premature delivery, low birth weight, intrauterine fetal death, and congenital malformations. The central hypothesis of this investigation is that the indigenous gram-negative bacterial flora associated with the oral cavity and/or the gut may play a role in birth complications in humans. We hypothesize that endotoxin, which is contained in high concentrations in both the oral periodontal flora and in the gut, may mediate abnormal pregnancy outcomes (APOs), especially in the presence of periodontal disease or increased penetration of endotoxin (lipopolysaccharide, LPS) at mucosal membranes. We propose experiments using the pregnant hamster model to determine how various routes, types, dosages and frequency of LPS challenges influence pregnancy outcome, mediator production and immune sensitization. Animals will be challenged with Bacteroides gingivalis (B.g.) either as whole cells, heat-killed or isolated LPS prior to mating and/or during pregnancy. Challenge will be either intravenously, by inoculation into a previously implanted subcutaneous tissue chamber, by oral periodontal infection model or by gastric intubation. We will determine the effects of various LPS exposure routes and dosage regimens on fetal weight, viability and frequency of malformation. Bacterial and LPS specific antibody responses will be determined in maternal serum, chamber exudate and colostral whey by ELISA and transimmunoblot techniques, measuring lgG, lgM, lgA and secretory lgA (slgA). Furthermore, we plan to determine if selected LPS-induced secondary mediators are present in the maternal serum, chamber exudate or the amnionic fluid. We will examine these fluids for the presence of lipid mediators including the prostaglandins and thromboxanes, and the monokine, tumor necrosis factor (TNF). The influence of immune sensitization on LPS-induced APOs will also be examined by passive immunization using antibody from immunized animals and by performing adoptive transfer of splenocytes from sensitized animals to pregnant animals prior to LPS challenge. By performing these experiments in C3H, LPS responsive and LPS non-responsive congenic mouse strains, the effects of genetically-determined LPS responsiveness on LPS elicited APOs will be determined and correlated with changes in inflammatory mediators.